Water-soluble polymers are used in various aqueous systems, for example, as mineral dispersants, as water-treatment additives for boiler waters, cooling towers, reverse osmosis applications, sugar refining, paper production, geothermal processes and oil wells, and as detergent additives acting as builders, anti-filming agents, dispersants, sequestering agents and encrustation inhibitors. Water soluble polymers also play a role in coagulation and flocculation for waste water and drinking water clarification, and are also useful in mining, dewatering, and similar systems. In aqueous systems, it is often desirable to know the level of polymer in the system. However, the level of active polymer is not simply a function of how much polymer has been added. The polymer may have adhered to a surface, may have flocculated out of the water with sediment, or the polymer itself may have decomposed. Because polymers generally add cost to processes employing them, it is desirable to be able to use them efficiently.
Various homopolymers, copolymers, and terpolymers are used for water treatment. For example, polyacrylic acid-based polymers are used as water treatment polymers, such as for the treatment of industrial cooling water to prevent corrosion and mineral deposits, or scale. Phosphonic acid derivatives (HEDP, AMP) are also useful for the delivery of both scale and corrosion inhibition. In addition, metals such as molybdenum and various phosphates can be applied in conjunction with copolymers to deliver corrosion inhibition. Similarly, acrylamide copolymers are used.
Generally, active water treatment polymers remove dissolved minerals from cooling water by complexing with the minerals. Over time, the complexation sites of the water treatment polymer molecules become saturated. The polymer molecules then become “bound” or inactive and are unable to remove any additional minerals from the cooling water.
To prevent corrosion and scale damage to machinery, as the water treatment polymers are inactivated they must be removed and replaced by active polymers. Thus, active polymers must be continually fed into the cooling water to replace the inactive polymers. Maintaining the proper feed level for the active polymers is essential for optimum performance of the cooling water system. An improper feed rate can lead to serious problems. For example, an insufficient amount of active polymer can result in the water treatment being overwhelmed by dissolved minerals, thereby causing severe corrosion or scale deposit. On the other hand, maintaining too high a level of the active polymer is expensive and results in an inefficient method for treating industrial cooling water.
Although several methods are available for determining the concentration of polymer in an industrial cooling water system, these techniques are unsatisfactory because they only determine the concentration of total polymer, i.e., active plus inactive polymer, and do not provide information regarding the concentration of active polymer alone. Moreover, available methods suffer from a lack of specificity and/or sensitivity. For example, existing methods for detecting water treatment polymers, such as sulfonated copolymers of acrylic acid (sulfonated copolymers), involve the use of colloid titration with PVSK (poly-vinyl sulfate potassium), complexation with Hyamine 1622, or reaction of excess magnesium with chrome azurol S.
The above tests detect any polyanionic material and do not distinguish between active and inactive polymer concentrations. In addition, these methods have a detection threshold of only about 50 ppm polymer. Therefore, the total amount of active sulfonated polymer in an industrial cooling water system cannot currently be inexpensively, rapidly or reliably determined.
Furthermore, currently available methods collect a sample at a given point in time, thereby providing the operator with only a snap shot rather than a moving picture in a highly dynamic system that is seeing a tremendous amount of change caused by chemical and physical stresses to the treatment polymer.
Cationic polymers are used in several areas of industrial water treatment such as paper manufacture, effluent stream clarification, sludge dewatering, mineral process and others. When discharged into the environment, excessive amounts of cationic polymers may be problematic. It is therefore desirable to know, with specificity and precision, the amount of residual cationic polymer in a sample prior to discharge. Many currently available methods of determining cationic polymer concentrations in waste water and other water treatment systems suffer from a lack of specificity or sensitivity as with the sulfonated copolymer detection methods described above. Therefore, highly sensitive methods having specificity for particular water treatment polymers and methods having the ability to provide real time measurements of available, active polymer are needed.